Film drive mechanism for motion-picture apparatus



Feb. 22, 1955 J. L PETTus 2,702,705

FILM DRIVE MECHANISM FOR MOTION-PICTURE APPARATUS Filed Jan. 1B, 1950knew L. B92117714' iff.; l WWW United `States Patent O i FILM DRIVEMECHANISM FOR MOTION-PICTURE APPARATUS James L. Petrus, Encino, Calif.,assignor to 'Radio Corporation of America, a corporation of DelawareApplication January is, 195o, serial No. 139,180 claim. (ci. r11-2.3)

This invention relates to motion picture equipment, and particularly toan automatic clutch starting unit or adjunct for the film driving systemof. a recorder or reproducer.

In motion picture recorders and reproducers, and particularly recorders,it is desirable that the film be accelerated up to its uniform speed inthe shortest possible time, since the film being advanced duringacceleration is not useable for recording sound, and usually more thanone recorder and one or more cameras are operating simultaneously. Insuch tlm sound systems, a very uniform film speed is desired, and one ofthe means for obtaining the required uniform speed is a heavy inertlaelement such as a flywheel driven by the pull of the film passing over aroller or drum. The motor can bring the geared, toothed sprocketsdriving the lm up to speed quite rapidly, but considerable time isrequired to bring the heavy flywheel mass up to uniform rotation solelyby the pull of the film.

Several devices in the form of clutches have been used to positivelydrive the ywheel during the acceleration period and then automaticallyrelease it, so that it can -be film driven thereafter and serve itspurpose as a film speed stabilizer. One such automatic mechanism isdisclosed and claimed in Black U. S. Patent No. 2,106,338 of January 25,1938, this system utilizing centrifugal force to actuate the clutchelements. The present type of clutch is of simplified form, and onewhich may be an adjunct attachable to most of the standard types ofcommercial film sound recorders. It utilizes a spring pressed clutchplate which may be moved into contact with the ywheel, the clutch platebeing positively driven from the motor drive. The clutch is actuatedelectrically, and, after its uniform speed has been reached, it isde-energized and allowed to separate from and free the ywheel.

The principal object of the invention, therefore, is to facilitate theacceleration of all the rotating elements of a lm drive to a uniformspeed in a short time period.

Another object of the invention is to provide an improved lm pulledflywheel drive for a lm advancing mechanism which is disconnected aftera predetermined time period.

A further object of the invention is to provide an improved clutchadjunct which may be attached to a lm driving apparatus for acceleratingthe ywheel at the same rate as the other rotating elements of thesystem.

Although the novel features which are believed to be characteristic ofthis invention will be pointed out with particularity in the appendedclaims, the manner of its organization and the Inode of its operationwill be better understood by referring to the following description,read in conjunction with the accompanying drawings, forming a parthereof, in which: t

Fig. l is an end view of the invention shown attached to a recorder.

Fig. 2 isa cross-sectional view taken along the line 2-2 of Fig. 1.

Fig. 3 is a schematic view of the electrical portion of the invention,and

Fig. 4 is a cross-sectional view of a modification of the invention.

Referring now to the drawings, in which the same numerals identify likeelements, a casing or housing 5 is attached by screws 6 to the casing orhousing 7 of a sound recorder or reproducer. The recorder or reproducerelements shown are a worin gear 9 driven by a motor 44, the gear 9 beingin mesh with a pinion 10 on ICC a shaft 11, and on which is a toothedfilm sprocket 12. As is well-known, the film is threaded over thesprocket 12 and around a film-pulled drum 14 on a shaft 15, and on whichis attached a ywheel 16. Upon acceleration of the sprocket 12, the filmnormally slips for a period over the drum 14 before the ywheel 16 is upto speed, which is some time after the sprocket 12 is at uniform speed.'The unit shown in the casing 5 is adapted to bring the ywheel up tospeed in the same short period of time as the sprocket 12.

Mounted in an internal boss 20 of the casing 5, are bearing sleeves 21,in which is a rotatable shaft 22, to which is attached a sprocket wheel23. The portion of shaft 22 to the right of the sprocket 23 is splinedto portion 24 of shaft 11, so that rotation of the shaft 11 positivelyrotates the sprocket wheel 23. ln the lower part of the housing 5, afixed shaft 26 is held in position by set screw 27 in an external boss28. Mounted on the shaft 26, is a rotatable sprocket wheel 30 with itshub 36 mounted on a bearing sleeve 31. A ladder chain 29 connectssprocket wheels 23 and 30. One end of the bearing sleeve abuts a rollerbearing 32, and its other end abuts one end of a coiled spring 33, theother end of spring 33 being positioned against a head 34 of the shaft26. Since the shaft 26 is xed, the spring 33 urges the sprocket 30 tothe left. Mounted on the sprocket wheel hub 36, is a disc 37, to whichis, attached a friction ring 38 which is normally maintained away orseparated from the left-hand surface of flywheel 16 by the spring 33.

To bring the friction disc 38 into contact with the ywheel 16, asolenoid relay 40 is energized, this relay drawing the end 41 of itsarmature downwardly, which moves the end 42 to the right. The relay coiland armature are mounted in a bracket 43, and the end 42 contacts aslidable collar 39. As the compression of the spring 33 is overcome, thering 38 contacts the flywheel 16, and the ywheel is then directlyconnected to the shaft 11 over sprocket wheels 23 and 30 and chain 29.The flywheel will be brought up to speed simultaneously with iilmsprocket 12.

Referring now to Fig. 3, the motor 44 is shown diagrammaticallyconnected across terminals 45, which are connected to an electricalpower source when a starting switch 46 is closed. Simultaneously, withthe energizing of the motor 44,-the solenoid coil 40 will be ener-vgized over a thermostatic switch 47, which is adjusted to open itscontacts at the end of the same time period required for the drivemechanism and film sprocket 12 to come up to speed. At this instant, thespring 33 will release the friction ring 38 from the flywheel and itwill be driven thereafter solely by the film pull.

The modification shown in Figs. 1 and 2 is one wherein the power isobtained internally of the recorder drive mechanism. In Fig. 4, amodification is shown wherein the sprocket-and chain drive iseliminated, and the clutch plate is driven externally by a beltconnected to another portion of the recorder or to an auxiliary motor.Referring now to Fig. 4, a casing 50 is attached by screws 51 to arecorder housing 52. The flywheel 54 is driven when the friction platev55 is pressed against its face by a disc 56 mounted on a hub 57 pinnedto a shaft 59 by a pin 60. The same relay 40 and armature 41-42 areillustrated, which, upon energization, will move the disc 56 andfriction ring 55 into contact with the flywheel 54. Pressure is appliedto the hub 57 through collar 62 and a bearing ring 63, and, against thetension of a coiled spring 65 positioned between the face of a boss 66and a hub 67 of a drive pulley 68, which is driven by a belt 69. Thesame energization circuit shown in Fig. 3 is used for the modificationshown in Fig. 4, so that the ihn when it is forced to slip too rapidlyover the rc` or reproducing I claim: Y

l. A mechanism for attachment to the housing of a iilm advancingmechanism provided with a film driven lywheel, comprising a casing; ashaft extending across said casing in position to be aligned with theaxis of rotation of said ywhcel, a shiftable clutch driving elementrotatably mounted on said shaft and adapted to engage said flywheel todrive the same; means interposed between said clutch element andflywheel for normally maintaining the same in disengaged position; asolenoid relay connected to said clutch element for causing said elementto engage said flywheel simultaneous with the commencement of theadvancement of the film in the mechanism; and means for declutching thesaid driving clutch element from said flywheel, the said meanscomprising an electric circuit connecting a motor and the said solenoidrelay through a thermostatic switch adjusted to open its contacts at theend of the same time period required for the film drive member to comeup to speed whereby said clutch engages said flywheel only during theperiod of acceleration of said mechanism.

2. A detachable film drive starting device for attachment to the housingof a film advancing mechanism provided with a rotatable film driveninertia element, the said drive starting device comprising a casingadapted to be secured to said housing opposite the said inertia element;a shaft extending across said casing in position to be aligned with theaxis of rotation ofv said inertia element when the said device ismounted in position of use; a driving friction disc carried on one endof said shaft; means whereby said disc may be `shifted into engagementwith the outer face of said inertia element, the said means includinginstrumentalities comprising an electrical circuit including athermostatic switch for shifting the said disc into engagement with theinertia element at the start of said film drive and shifting said discand inertia element out of engagementafter said film drive has staccelerating.

The device as claimed in claim 2 wherein the means for shifting the saiddisc into engagement with the said inertia element comprises apivotedbell-crank lever one end of which is adapted to exert pressure onthe said disc to shift they same mto coupling engagement with saidinertia element and the other end of said levery consists of anarmature; and a solenoidiuxtaposed to said armature for actuating thesame.

4. The combination with a motion picture recorder and reproducer comrising a housing in which are mounted a motor driven drive shaft and afilm driven shaft extending parallel to said drive shaft and having atlywheel mounted on the end thereof, of a clutch startin unit forquickly bringing the said ywheel to the for the normal o ration of thedrive. the said unit comprising acaslng detachably secured to saidhousing and acrosswhich extends a rst shaft ably secured to an end ofthe said nlm drive shaft: a gearing carried by the said lirst shaft; asecond shaft extending across said casing; a clutch element in the formof a friction plate including a gearing slidably mounted on said secondshaft, the said element being spring biased out of operative positionand juxtaposed to said flywheel toY engage a side'face of the same;means connecting the gearing aforesaid; a solenoid relay positioned toshift the said clutch element into clutching engagement with saidfiywheel at the start of said ilm drive; and an electric circuit.connecting the said relay through a thermostatic switch adjusted to openits contacts at the end of thesame time period required for the iilmdrive member to come up to speed, whereby the slidable clutch memberwill automatically be restored to nonoperative position when theoperating speed has been reached.

5. A detachable film drive starting device for attachment to housing ofa film advancing mechanism provided with a lm advancing element drivenby an electricmotor and a lm pulled element having a ywheel thereon,

-the said drivecomprising a casing adapted to be to said housingopposite the said ywheel; a shaft journaled in said casing and adaptedto be connected to a driven shaft of said mechanism; a sprocket on saidshaft; a second shaft journaled in said casing, the said shaft Vcarrying on one end thereof a combined sprocket and driving clutchelement and being adapted to be aligned with the shaft carrying saidywheel; a spring interposed between said flywheel shaft and saidcombined sprocket and driving clutch element for maintaining the latterout of clutching engagement with said ywheel; a sprocket chain trainedover said sprockets; and means to shift said combined sprocket anddriving clutch element into engagement with said flywheel, the saidmeans comprising a pivoted bell-crank lever one end of which is adaptedto exert pressure on said combined sprocket and driving clutch elementto shift the same into engagement wit said flywheel and the other end ofwhich consists of an armature; a solenoid juxtaposedto said armaturefor` actuating the same; a thermostatic switch; the said solenoid, andswitch being electrically connected with said electric'motor so thatsaidmotor, switch and clutch are actuated simultaneously; and the saidswitch being ad `iusted to close its contacts at the start and to openits contacts at the end of the same timeperiod required for the lm drivesprocket to come up to speed, whereby the driving clutch element willautomatically be restored to nonoperative position.

. References Cited in the ille of this patent UNITED STATES PATENTS1,908,786 Pioch 2,098,215 Black Nov. 9, 1937 2,106,338 Black Ian. 25,1938

